The nature and properties of collagen precursors (procollagen) synthesized by different connective tissue cells in culture is being investigated in order to determine the exact sequence of events in collagen synthesis and modification. Many heritable and acquired connective tissue disorders are related to an inability to complete the collagen synthetic and maturation pathway. Thus, we hope by studying cells from normal and diseased tissues in culture to be able to relate biochemical findings of the nature of the procollagen to the specific disease in question.